When drugs are to be injected into the human body, it is essential that the dose set by the user is the actual dose injected. If this is not the case, the medicating of the patient is not correct, which in some cases can have serious or even fatal consequences. In order to ensure that the dose selected by a dose setting member does not exceed the remaining amount of medication in a reservoir in a syringe device, an end-of-content mechanism may be provided.
End-of-content mechanisms are known in the art. One such example may be seen in WO 01/19434 A1 which discloses a limiting mechanism for an injection device. A dose is injected by rotating a dose setting member which during this rotation carries a driver with it to rotate this driver which moves a piston forward. The driver is provided with a track having a length which is engaged by a track follower coupled to the dose setting mechanism.
Another example may be seen in WO 2004/007003 A1.
U.S. Pat. No. 5,938,642 disclose an injection device comprising a driver, a nut and a threaded piston rod. During dose setting the nut is rotational screwed up the threaded piston rod and during dosing the nut and the piston rod is brought axial forward the same distance. Once the nut reaches the end of the thread of the threaded piston rod no further dose can be set.
It is an object of a preferred embodiment of the present invention to provide an alternative to the above solution. Especially, it is an object of the present invention to provide a solution which allows an outer surface of a driver to be directly coupled to the inner surface of a drum scale, and thus it is an object of the present invention to provide an end-of-content mechanism which may be positioned in the space defined by the inner walls of a driver.